Global input override between overlay applications

[cathiecode]

Hi. This is a feature request that allows us to block input for overlays by another overlay app.

I'm developing a new text input system that works with overlay tools such as XSOverlay or OVRToolkit. For that, I tried to use a feature that is introduced in #1236, "Enable global input from overlays". However, the API is not very useful for overlay apps that want to block the input of another overlay app. This is because "Global Input" action set does not override another one in a different process.

If the API allows us to override other Global Input actions, it could be more useful for overlay apps that work for other overlay apps. Also, this behavior is more suitable for a feature named "Global Input".